I was at DSA last week for the third time this year, and didn't have any problems whatsoever - already checked in online so went straight upstairs, breezed through security with no queuing at all. My Manchester-purchased plastic liquids bag was fine for them and the security staff were rather pleasant - so much so that it surprised me, and the person I was travelling with actually commented on how friendly they were! Maybe you just caught someone on an off day...
Also, if you were THAT annoyed, why not direct your comments at the airport instead of an internet forum?